Wavefield imaging of nonlinear ultrasonic Lamb waves for visualizing fatigue micro-cracks

Haiming Xu; Lishuai Liu; Xuan Li; Yanxun Xiang; Fu-Zhen Xuan

doi:10.1016/j.ultras.2023.107214

Wavefield imaging of nonlinear ultrasonic Lamb waves for visualizing fatigue micro-cracks

Ultrasonics. 2024 Mar:138:107214. doi: 10.1016/j.ultras.2023.107214. Epub 2023 Dec 2.

Authors

Haiming Xu¹, Lishuai Liu², Xuan Li¹, Yanxun Xiang³, Fu-Zhen Xuan¹

Affiliations

¹ Shanghai Key Laboratory of Intelligent Sensing and Detection Technology, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China.
² Shanghai Key Laboratory of Intelligent Sensing and Detection Technology, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China. Electronic address: lishuai.liu@ecust.edu.cn.
³ Shanghai Key Laboratory of Intelligent Sensing and Detection Technology, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China. Electronic address: yxxiang@ecust.edu.cn.

PMID: 38056320
DOI: 10.1016/j.ultras.2023.107214

Abstract

The traditional nonlinear ultrasonic technique, as typified by the second-harmonic generation and the frequency mixing response, can be employed to identify and characterize the micro-damage. However, the research on micro-damage characterization using nonlinear Lamb wave imaging technique remains an ongoing challenge and is rarely reported. A method called standardized amplitude difference is proposed for nonlinear feature enhancement, and further for fatigue crack imaging based on the wavefield data. Wavefield data contain abundant information on the spatial and temporal variation of propagating waves in the damaged structure. The nonlinearity index β^' of the signal difference under the high and low incident wave amplitudes is calculated for fatigue crack imaging. Two scanning methods, including local scanning and global scanning, are introduced to image the fatigue crack tip and visualize the wave field of the harmonics respectively. The experimental validation, based on the imaging results of an aluminum alloy plate specimen with a barely visible fatigue crack and a steel plate with a blind hole, manifests that the proposed method can be used to enhance and extract the nonlinear features and suppress the fundamental frequency, so as to improve the signal-to-noise ratio (SNR) of the micro-damage imaging results.

Keywords: Closed fatigue crack; Laser interferometer; Nonlinear Lamb waves; Wavefield data.